Critical Period of Weed Competition / Nutrient Losses

  • when the rice plants are in the vegetative phase and the yield components of the rice plant are being determined
  • Worldwide yield losses attributed to weeds average approximately 10%, while on individual fields, losses may range from 40 to 90 per cent.
  • Competition varies widely from situation to situation and from culture to culture - Short weeds and those that germinate late in the cropping season tend to compete less than tall weeds or those that germinate at the beginning of the cropping season.
  • Critical period for rice-weed competition is up to 1 to 6 weeks after transplanting

Critical Period of Nutrient Losses

  • Most severe during the first half of the rice growing season- From un-weeded control plots, based on the the experiments at DRR, the NPK uptake by transplanted rice was found to be in the range of 23-32, 4-8 and 48-65 kg / ha, respectively, while removal by weeds, was in the range of 8-15, 3-5 and 15-28 kg/ha, respectively.
  • in wet-seeded rice system, in non-weeded control plots, the nutrient removal by weeds was more than that of transplanted rice, which was estimated to be in the range of 34-51, 5-8 and 39–53 kg NPK, respectively.